This invention relates to lead frames and, it relates, more particularly, to lead frames mechanically reinforced by mechanical nodes as well as a process for the production of such lead frames.
In the case of many electrical leads, it is necessary for more than one semiconductor configuration to be assembled on a lead frame. At the same time, it is required, upon completion of the assembly work, for at least one electric terminal to be brought out of the package encapsulating the lead separately. For example, in the case of conductive strip LED displays, eight discrete semiconductor chips per indicating element (digit) must be assembled on a lead frame. At the same time, at least one electric terminal per semiconductor chip must be brought out of the display package separately. This results in a terminal arrangement that is highly intricate so as to be an unstable chip carrier.
One difficultly which arises with display leads is that they must be bent in a U-shape prior to assembling. In this respect, as a result of the required conductive strip configuration, problems caused by the fanning out of unused terminal arise in the plane of the lead frame as well as in the terminal position.
In this situation, these problems were responsible for total breakdown during production and early breakdowns at the installation site, caused by wire stress. So far, there has been an attempt to solve these problems prior to assembling the lead by applying to the lead frame a stabilizing and electrically insulating reinforcement material such as a foil or film or resin.
There has also been one approach to solve this problem by embedding the lead frame in thermoplastic or duroplastic plastics. This also introduces problems. Among them are increased costs, inadequate temperature stability during processing, and inadequate cleanliness of the bonding planes.
There is another approach to solve these problems by means of different frame concepts, for example, by using a pc board instead of a lead frame. This in turn, produces new problems associated with the high costs of material and assembly.